5-Alkylidene-hexahydro-1H-cyclopenta[c]pyrrol-1,3-diones by nickel(0) or palladium(0) catalyzed [3+2] cycloaddition of methylenecyclopropanes with maleimides
作者:Paul Binger、Andreas Freund、Petra Wedemann
DOI:10.1016/s0040-4020(01)80117-4
日期:1989.1
Nickel(0) catalyzed [3+2] cycloaddition of methylenecyclopropanes 1a - e with N-substituted maleimide 3b (R = CH3) and 3c (R = Ph) leads almost exclusively to the title compounds 6 and 7. The same reaction occurs in the presence of a palladium(0) catalyst with lower selectivity. Neither unsubstituted maleimide (3a) nor maleic anhydride (2a) undergo this metal catalyzed cycloaddition. With isopropylidenecyclopropane
Rate Enhancement in Ethanolic Aqueous Buffer. The Diels-Alder Reaction
作者:Michael B. Smith、Joseph N. Fay、Young Chan Son
DOI:10.1246/cl.1992.2451
日期:1992.12
We have observed a 2.5-3-fold increase in the rate of Diels-Alder reactions when done in aqueous ethanol, where the aqueous solution was prepared with a pH 7 buffer. This is a simple, inexpensive and convenient method for modest acceleration of the Diels-Alder reaction, in addition to the rate increase normally observed in aqueous media.